Foams are often used in the petroleum industry such as in drilling, fracturing, hydrocarbon lift or foam assisted lift (FAL) due to advantages offered by their low density and their special rheological behavior. In all these applications high foam stability, often in harsh conditions (high temperature, high pressure) is important and a challenge. A particular problem is that in these processes very often both water and oil phases are present in high concentrations and the presence of oil (hydrocarbon) is often detrimental to foam stability. This is particularly important in FAL. It is a common problem in gas wells that they get partially plugged by liquid and it is estimated that out of the more than 400,000 gas wells in the US about 80% suffer from liquid loading. The most often used gas well deliquification method is to inject foamants (with a capillary or other methods) into the liquid plug so that the gas flow converts it into a foam and drives it out of the well. If the hydrocarbon to water ratio is high (more than about 10-20%) then the hydrocarbons are highly detrimental to foam stability and the currently used foamants cannot create a foam stable enough and the method fails.
U.S. Patent Publication 2007/0079963 describes a process of producing foam from a wet hydrocarbon, using a foamant comprising a siloxane. The siloxane is defined as a polysiloxane, ethoxylated, propoxylated or ethoxylated-propoxylated siloxanes and their combinations. The molecular weight of the siloxanes is specified as about 1000 to about 1,000,000 daltons and in a preferred range, 6000-60,000 daltons. In the examples (Table 3) the experiments were not successful with a 600 MW siloxane, but they were successful with a siloxane of 6000 MW and the authors concluded that the optimum is in the 6000-60,000 MW range, depending on the conditions under which it will be used. The siloxane can be also combined with organic surfactants (non-ionic, anionic, cationic). The process can be used in gas-lifted oil wells, gas-wells etc.
It is nevertheless advantageous to provide a foaming composition which is effective in the presence of high amounts of liquid hydrocarbons.